Process for preparation of internal olefins



r 3,267,167 Ice Patented August 16, 1966 3,267,167 PRGCESS FOR PREPARATION 0F INTERNAL OLEFINS Richard Waack, lFramingham, Mass., assiguor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware No Drawing. Filed July 17, I963, Ser No. 295,846 18 Claims. (Cl. 260-4577) This invention relates to an improved process for the formation of internal olefins by the reaction of a halopolyfluoro methane with an organo lithium compound. More specifically, it relates to such a process in which the yield of such internal olefins is improved by maintaining an excess of the halopolyfluoro methane.

The production of internal olefins, such as nonene-4, has been disclosed by V. Franzen, Angrew. Chem. 72, 566 (1960), who teaches the addition of dibromodifluoro methane to at least 3 moles of an organolithium compound such as butyl lithium to give internal olefins.

In a later article by V. Franzen and Belle Fikentscher, Chemische Berichte, 95 pages 1958-1963 (1962), the ratio of 3 moles of organometal compound per mole of difiuorodibromo methane (or trifiuorobromo methane) is again used to give the internal olefin. The authors point out that the trifluorobromo methane reacts with butyl lithium at 70 C. to give a yield of 62% 4-nonene, based on the butyl lithium. Here again, the proportions are 3 moles of butyl lithium to one mole of the trifluorobromo methane.

In this same article it is pointed out that the difiuorodibromo methane is added dropwise to a solution of butyl lithium in ether at 70 C. to give a violent reaction at every drop of the former and that the reaction occurs with about 0.35 mole of the difluorodibromo methane per mole of the butyl lithium. This proportion is the same as previously indicated, namely, about 1 mole of the difluorodibromo methane per 3 moles of butyl lithium.

In the table of results, these authors indicate that the yield of olefin for this reaction is 67% when the difiuorodibromo methane is used and 62% when the trifluorobromo methane is used. In the only other similar reaction reported, octyllithium is shown to give a 54% yield of the corresponding internal olefin. While reference is made to good yields, there is no yield for this type of reaction shown to be above 67% based on the weight of butyl lithium consumed in the reaction.

The authors indicate that the corresponding reactions proceed as follows:

In both of these reactions, 3 moles of butyl lithium are used per mole of the halopolyfluoro methane. In each of the experiments described in this article, the fiuorobromo methane is added dropwise to the organometal compound in ether as a solvent. Therefore, there is always excess organometal compound during the reaction period, that is even more than the 3 to l proportion. In other words there is never any excess of the methane derivative but in fact less than the proportion in which it is ultimately consumed.

In Experiment 3, while reference is made to the use stated that the CF Br is added dropwise to the butyl of 0.5 mole of CF Br to 0.1 mole of butyl lithium, it is lithium and that a violent reaction takes place. Therefore, during the course of the reaction, the butyl lithium is in excess and since there is a violent reaction, it is consumed before there is any excess of the CF Br added.

In accordance with the present invention, it has now been found surprisingly that whereas yields of no more than 67% are obtained by the methods of the above-cited references, the yield of internal olefins based on the amount of alkyl lithium consumed can be increased to 90% or more by adding the butyl ltihium to the halopolyfluoro methane, e.g. difiuorodibromo methane, trifluorobromo methane, etc., so that an excess of the halopolyfluoro methane is maintained during the reaction period. In view of the fact that three moles of the alkyl lithium is required for reaction with each mole of the halo methane, it is unexpected that the yield would be as good by applicants process as compared to the process shown in the reference. Most surprisingly, however, it is found that the process of adding the fiuorobromo methane to the alkyl lithium, that is having excess halo methane in the reaction mass, gives markedly superior results in the yield of the desired internal olefin.

The higher yield of olefin in these reactions is remarkable considering the fact that the intermediate difluorocarbene must react with two moles of butyl lithium in competition with a large excess of the fiuorobromo methane. Therefore, it is unexpected that the lower concentration of butyl lithium will give improved yields of the desired olefin and that the large excess halopolyfluoro methane (Freon) does not react with the butyl lithium and interfere with the difluorocarbene (CF reaction.

While the overall amount of reagents used can be in the ratio of three moles of butyl lithium to one mole of the fiuorobromo methane, the fact that the butyl lithium is added gradually to the fiuorobromo methane assures that there is always an excess of the latter reagent and that it is not until the last drop of butyl lithium is added to the reaction mass that there is reached the true ultimate reaction proportion of 3:1 moles.

Various solvents which have solvent power for the reagents and advantageously for the olefin product can be used in this reaction period provided they are inert toward the reagents and the desired product. However, it is preferred that the solvent has a boiling point high enough as not to be too rapidly vaporized by the resultant exothermic reaction. The solvent also must have an appropriate melting point so that the solvent does not freeze at the low temperatures used in this particular reaction. A particularly suitable solvent is n-hexane, as well as similar aliphatic hydrocarbons of appropriate boiling point and melting point. Ether can be used although it has such a low boiling that the exothermic reaction generally produces a violent vaporization of the ether as the butyl lithium is dropped into the reaction mass. Higher boiling ethers, such as tetrahydrofurane, are generally more suitable.

The temperature and pressure conditions of the reaction system are not critical. It is only necessary that the conditions be such as to retain the reagents in solution, and that the temperature is above the freezing point of this system and below the boiling point of the reagents at the pressure involved. The reaction time is very short as evidenced by the fact that the inorganic byproducts are precipitated almost immediately. The rate of addition is advantageously slow enough to avoid excessive boiling of the solvent by the exothermic heat of the reaction. Generally, temperatures in the range of '80 C. to room temperature are advantageous, with an appropriate selection of solvents having boiling and freezing points to accommodate the reaction. Generally, however,

it is desirable to operate below C. so that the exothermic heat is more quickly absorbed and, if there is any boiling of the solvent, that it can be kept under control with a moderate reflux rate.

Addition of the organolithium compound at too rapid a rate will result in a violent exotherm and also a reduction in the yield since excess organolithium even in a limited portion of reaction mass defeats the purpose of applicants invention, namely the maintenance of an excess of the Freon.

As previously stated, the solvents are selected according to appropriate solvent power, appropriate melting and boiling points, and non-reactivity with the reagents. Particularly suitable solvents are the aliphatic hydrocarbon and aliphatic ethers such as hexanes, heptanes, pentanes, octanes, cyclohexane, cycloheptane, die-thyl ether, dioxane, diisopropyl ether, the diethyl ether of ethylene glycol tetrahydrofurane, etc. Preferably such solvents have 4-8 carbon atoms.

The halopolyfiuoro methanes which can be used in the practice of this invention are referred to generally as freons. Appropriate compounds include those in which there are two or three fluorine atoms and one or two other halogen atoms, namely bromine, chlorine or iodine in the molecule. .Typical compounds include difiuorodibromo methane, difiuorobromo methane, difiuorochloro methane, difluorodichloro methane, trifluorobromo methane, trifluorochloro methane, difiuorodiodo methane, difluoroiodo methane, trifluoroiodo methane, or any difluoro carbene (CF generator.

The organolithium compounds that can be used in the practice of this invention are the aliphatic, or arylaliphatic hydrocarbon lithium compounds, including those having ethylenic or acetylenic unsaturation therein. Typical compounds include butyllithium, amyllithium compounds, ethyllithium, methyllithium, cyclohexyllithium, propyllithium, benzyllithium, phenethyllithium, cyclohexylmethyllithium, cyclohexylethyllithium, cyclopentylmethyllithium, vinyllithium, allyllithium, butenyllithium, ethynyllithium, propargyllithium, etc. Advantageously, the organo group contains no more than about carbon atoms.

The internal olefins produced by the practice of this invention generally have an odd number of carbon atoms therein by virtue of the fact that two identical groups of the organolithium combine with the one carbon atom from the difluorocarbene resulting in an odd number of carbon atoms. However, it is possible to produce mixtures in which some portion of the product has an even number of carbon atoms. For example, a mixture of organolithium compounds can be used in which one compound has an even number of carbon atoms and the other compound has an odd number of carbon atoms. In this way some of the hydrocarbon radicals of the odd numbered carbon atoms will end up in the same compounds with hydrocarbon radicals of the even numbered carbon atoms plus the carbon from the carbene compound with a resulting even number of carbon atoms.

Typical examples of olefins that can be produced by the process of this invention include: none-4, undecene-S, tridecene-6, pentadecene-7, heptadecene8, nonadecene-9 and heneicosene-lO, 1,3-diphenyl-propene, 1,5-diphenyl pentene-Z, propylene, pentene-Z, heptene-3, heptatriene- 1,3,6, nonatriene-l,4,8, heptene-3,-diyne-l,8, etc.

The invention is best illustrated by the following examples. These examples are given by way of illustration and are not intended to limit in any way the scope of the invention nor the manner in which it may be practiced. Except where otherwise specifically provided, reference to parts and percentages are to parts and percentages by weight respectively.

Example I To a dry, 3-neck 250 ml. flask equipped with an argon inlet, a condenser cooled with ice and having a gas outlet at the top, a stir-ring rod operated by magnetic stirring and a pressure equalizing dropping funnel, is added under an argon atmosphere, a solution of 23.6 ml. (0.250 moles) of dibromodifiuoro methane in 10 ml. of dry spectrograde n-hexane, which has been cooled in ice water. To this is added dropwise over a two hour period a solution of 84 ml. (0.125 moles) of n-butyl lithium in n-hexane. The reaction mass is cooled with ice during the period of addition, but after the addition of the butyl lithium is completed, the ice bath is removed and stirring is continued for one hour while the reaction mass is allowed to come to room temperature. The reaction mass is centrifuged to recover the insoluble lithium salts, which are twice washed in 25 ml. portions of n-hexane. The wash liquid is added to the reaction solution, which is thereafter fractionally distilled to give a yield of 91% nonene-4, based on the butyl lithium.

Example II Similar results are obtained when the procedure of Example I is repeated using in place of the difluorodibromo methane an equivalent amount of difiuorobromo methane, difiuorochloro methane, difluorodichloro methane, difiuoroiod-o methane, trifluorobromo methane, and trifluorochloro methane respectively.

Example III The process of Example I is repeated a number of times using in place of the butyllithium, the following lithium compounds: n-propyllithium, ethyllithium, n-pentyllithium, n-hexyllithium, benzyllithium, allyllithium and propargyllithium.

Yields of over based on the organometal compounds are obtained in every case. The products obtained are respectively: n-heptene-3, n-pentene-Z, n-undecene-5, ntridecene-6, 1,5-diphenyl-pentene-2, n-heptatriene-1,3 ,6, and n-heptene-3 -diyne-1,8.

While the normal alkyl radicals are used in the foregoing examples, it is also possible to use aliphatic hydrocarbon groups in which there is side branching. However, the carbon atom to which the lithium is attached is preferably a primary carbon atom since such compounds are more stable and easier to prepare.

While certain features of this invention have been described in detail with respect to various embodiments thereof, it will, of course, be apparent that other modifications can be made within the spirit and scope of this invention and it is not intended to limit the invention to the exact details shown above except insofar as they are defined in the following claims.

The invention claimed is:

1. A process for the preparation of an aliphatic hydrocarbon compound having an ethylenic group at least one carbon atom removed from each end of said aliphatic compound comprising the steps of reacting in an inert atmosphere an organo lithium compound and a halopolyfluoro methane selected from the class consisting of difluoro and trifiuoro methane compounds having at least one and no more than two other halogen atoms therein and having a total number of halogen atoms therein of no more than four, said organo radical in said organo lithium compound being an aliphatic hydrocarbon radical selected from the class consisting of aliphatic hydrocarbon radicals and aryl and cycloalkyl derivatives thereof, in which radicals the carbon atom to which said lithium is attached is in turn attached to no more than one carbon atom, and said organo lithium compound being 4. A process of claim 2 in which said solvent is n-hexane.

5. A process of claim 1 in which said reaction is conducted at a temperature of no less than 80 C. and no more than a temperature which initially is no more than room temperature and the ambient temperature caused by the exotherm of the reaction not allowed to reach a temperature exceeding the boiling point of a solvent having no more than 8 carbon atoms therein and selected from the class consisting of aliphatic hydrocarbons and aliphatic ethers.

6. A process of claim 1 in which said reaction is conducted at a temperature in the range of no less than 80 C. and no more than about 0 C.

7. A process of claim 1 in which said halopolyfiuoro methane is dibromodifiuoro methane.

8. A process of claim 1 in which said halopolyfluoro methane is trifluorobromo methane.

9. A process of claim 1 in which said halopolyfluoro methane is dichlorodifluoro methane.

10. A process of claim 1 in which said halopolyfluoro methane is chlorotrifluoro methane.

11. A process of claim 1 in which said alkyl lithium is n-butyl lithium.

12. A process of claim 1 in which said alkyl lithium is n-amyl lithium.

13. A process of claim 1 in which said alkyl lithium is n-hexyl lithium.

14. A process of claim 1 in which said halopolyfluoro methane is dibromodifiuoro methane and said alkyl lithium is n-butyl lithium.

15. A process of claim 1 in which said halopolyfiuoro methane is dibromodifluoro methane and said alkyl lithium is n-amyl lithium.

16. A process of claim 1 in which said halopolyfluoro methane is dibromodifluoro methane and said alkyl lithium is n-hexyl lithium.

17. A process of claim 1 in which said halopolyfluoro methane is dibromodifluoro methane, said alkyl lithium is n-butyl lithium and said reaction is conducted in n-hexane.

18. A process of claim 17 in which said reaction is conducted at a temperature in the range of C. to 0 C.

No references cited.

ALPHONSO D. SULLIVAN, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,267,167 August 16, 1966 Richard Waack It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, lines 1 and 2, strike out "stated that the CF Br is added dropwise to the butyl of 0.5 mole of CF BT to 0.1 mole of butyl lithium, it is" and insert instead of 0.5 mole of CP Br to 0.1 mole of butyl lithium, it is stated that the CF Br is added dropwise to the butyl column 3, line 59, for "none-4" read nonene-4 Signed and sealed this 1st day of August 1967.

(SEAL) V Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A PROCESS FOR THE PREPARATION OF AN ALIPHATIC HYDROCARBON COMPOUND HAVING AN ETHYLENIC GROUP AT LEAST ONE CARBON ATOM REMOVED FROM EACH END OF SAID ALIPHATIC COMPOUND COMPRISING THE STEPS OF REACTING IN AN INERT ATMOSPHERE AN ORGANO LITHIUM COMPOUND AND A HALOPOLYFLUORO METHANE SELECTED FROM THE CLASS CONSISTING OF DIFLUORO AND TRIFLUORO METHANE COMPOUNDS HAVING AT LEAST ONE AND NO MORE THAN TWO OTHER HALOGEN ATOMS THEREIN AND HAVING A TOTAL NUMBER OF HALOGEN ATOMS THEREIN OF NO MORE THAN FOUR, SAID ORGANO RADICAL IN SAID ORGANO LITHIUM COMPOUND BEING AN ALIPHATIC HYDROCARBON RADICAL SELECTED FROM THE CLASS CONSISTING OF ALIPHATIC HYDROCARBON RADICALS AND ARYL AND CYCLOALKYL DERIVATIVES THEREOF, IN WHICH RADICALS THE CARBON ATOM TO WHICH SAID LITHIUM IS ATTACHED IS IN TURN ATTACHED TO NO MORE THAN ONE CARBON ATOM, AND SAID ORGANO LITHIUM COMPOUND BEING ADDED TO SAID HALOPOLYFLUORO METHANE WITH THE PROPORTIONS OF THE RESPECTIVE REAGENTS BEING MAINTAINED SO THAT THE HALOPOLYFLUORO METHANE IS ALWAYS IN STOICHIOMETRIC EXCESS OF SAID ORGANO LITHIUM COMPOUND. 